It is desirable that a machine give the user the opportunity for solution of the user's problems as easily, intuitively, and fast as possible. In the particular area of postage meters (franking machines) the user may need to configure the meter generally, or may need to set up the meter for applying some postage value to a particular mail piece.
Historically, most postage meters have keyboards with dedicated keys. Dedicated keys are simple to use. But in the modern global marketplace it is desirable to be able to serve many markets (with differing languages and regulatory requirements) with minimal or no hardware changes.
One approach is to provide a large touch screen, typically with a graphics display. The large touch screen may make it unnecessary to provide a separate physical keyboard at all. But a large touch screen is expensive, and can be fragile. For some repeatedly executed keyboard functions it may be desirable to retain at least some physical keys separate from the screen, even if other functions are carried out on the touch screen.
Still another approach is to provide "soft keys", which are keys devoid of any physical labeling, juxtaposed with a large screen (typically a graphical liquid crystal display screen), a portion of which is dedicated to providing labels for the keys. In this way, a set of soft keys can have one set of meanings (and labels) in one context, and may have a different set of meanings (and labels) in another context. The result is to reduce the number of keys needed, and is also to provide some capability to modify the machine for use in different countries.
One such postage meter system is shown in U.S. Pat. No. 5,437,010 to Blackman et al.
But in the particular area of low-end (inexpensive) postage meters, none of these approaches is ideal. A large graphical display screen is expensive. In many man-machine interface designs, not enough attention is paid to the fact that some user tasks are repeated with the same parameters or user inputs.